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diy solar

diy solar

Developing a new BMS, feedback wanted...

.....err....Aishi caps.......I got a lot of bad experience with Aishi brand. I remembered back in the day, I replaced all leaking + bulging Aishi caps on CFL, PSUs and monitors. I lost my soldering skill now though.......

Man, back in the day, compact fluorescent lamp was not potted and it is easier to solder the caps.....
Our EE used them on some other projects and liked them, and I don't have an opinion one way or the other - if we have any issues with them we'll certainly swap them out, and I'll keep an eye on them since you pointed them out. Like @Hedges said, sometimes it's hard to say with these companies that had poor products in the past, whether they still do or that's just more a reflection of the time and their quality in the past.

That is a WHOLE lot of connectors!
Do you daily play tetris? ;)
Really interesting project. When I read what you write, and how you write, I feel that you do this with great passion but most important with critical mindset and quality strive. Great work!
heheh, this board is a beast - I wanted it to cover all of our use cases, and it certainly does that and then some - and this board should be able to do some things that are pretty unique, I wasn't trying to just make another JK or JBD. Personally I love programming and working on cool projects, and so when the idea was floated for us doing the BMS I jumped at it. If you think the board is over the top, wait until you see our software stack. ;) I love products that are made by people who are actually passionate about them - maybe they aren't the best overall solution, but the solve a more vertical problem exceptionally...
 
Curious:

With the Transistors and connectors oriented like what, how do you mount heatsink to it?
And how do you orient it on a battery box?
So the back is also covered with components, so the heatsync will be on both the front and back - a bit like the JDB's do it, with an aluminum plate that screws down to make contact. Really it's the right side (where the battery terminals are) that needs the heat dissipation more than the left side, and we have done the thermal modeling to see how it should heat, but ultimately when it's under real load it's nice to see it happen in the real world. As I said, even at 100-150a it should be fine without heat syncs, but you wouldn't want to push it beyond that.

In terms of how it would be oriented for cases, it's designed to go into our systems, so I don't have any experience with other cases that are out there - we did match up a couple of the screw holes to a similar JK BMS, so you might be able to use the same mounting points, although the cable attachments might need to be different. We really didn't design it to be a drop in replacement for a JK or JBD, etc - so that's probably not going to be the best use case for it, you're probably better off just sticking with whatever the case is designed for. At some point we may design a rack mount case specifically for this, but that's a ways off as we do more software and hardware design work and not mechanical engineering.

FWIW, I've designed a 3D printed Eve 280-300ah prismatic cell holder, like those ABS one you can buy from China, and I'll be posting up the STL and pictures in a couple weeks for anyone who's interested in making anything like that. I print them with PETG, and assuming you're getting a decent price on your filament, it comes out to about the same cost as the Chinese ones, but when you factor in not paying for shipping it's much cheaper - plus it's fun to print them and mine have some different design elements I think are cool. We use 80/20 quite a bit, so they're designed to 'lock' into the channels on the 15 series (both from the bottom and top), and the sides of the brackets lock into eachother as well - and I just use fiber reinforced tape around it to keep it kind of locked together until it's mounted into the 80/20. On the top the channels also ensure that the 80/20 can't come in contact with the terminals, which would clearly be bad. ;)
 
If you think the board is over the top, wait until you see our software stack. ;)
I think you might misunderstood me a tiny bit.
It is crystal clear that your project strives/offers considerably more than what is available on the market.
Never the less, I think there are quite some DIY people that have mentality "Never enough, give us even MORE options!" 🤪
Any one disagree on that point?
solve a more vertical problem exceptionally...
Uuuh!
For me, the language (as in tool for communication between people), is just like a big box of LEGO. And I love to more or less constantly in every day life, strive using words as Lego pieces and convey my thoughts to the world either as precise or as creative as I can.
So, I just loved to read that sentence!
Clearly written by a "programmer/coder person". Yet so concise, precise and elegant! :)
 
150a may be enough, but 200a is nice for 280ah cells.

What is the closed comms programming like? What commands are there that the bms can do?
Will it be compatible with EG4, Sol-ark, Growatt, Midnite Solar?
 
FWIW, I've designed a 3D printed Eve 280-300ah prismatic cell holder, like those ABS one you can buy from China, and I'll be posting up the STL and pictures in a couple weeks for anyone who's interested in making anything like that. I print them with PETG, and assuming you're getting a decent price on your filament, it comes out to about the same cost as the Chinese ones, but when you factor in not paying for shipping it's much cheaper - plus it's fun to print them and mine have some different design elements I think are cool. We use 80/20 quite a bit, so they're designed to 'lock' into the channels on the 15 series (both from the bottom and top), and the sides of the brackets lock into eachother as well - and I just use fiber reinforced tape around it to keep it kind of locked together until it's mounted into the 80/20. On the top the channels also ensure that the 80/20 can't come in contact with the terminals, which would clearly be bad. ;)
you should start a separate thread to discuss this. Post some pics.
 
FWIW, I've designed a 3D printed Eve 280-300ah prismatic cell holder, like those ABS one you can buy from China, and I'll be posting up the STL and pictures in a couple weeks for anyone who's interested in making anything like that.
Oh, yes please!
 
150a may be enough, but 200a is nice for 280ah cells.
I interpret the 100-150a with out heat sink. But the aluminum plates are planned further in to development.
even at 100-150a it should be fine without heat syncs
I think we are all eager and looking forward to information about maximum continuous and short term currents, with heat sink, both calculated and revised after your initial tests.
 
Regarding heat sink and heat transfer from FETTs got me thinking about CPUs and thermal paste.

First of all, I have learned that even really good paste have slower heat transfer compared to say copper or even aluminum? Anyway, the function of paste is to bridge all the area of connected components, because there is always thousands of tiny scratches on every surface (scratches - air - thermal insulation). So, the layer of the paste between components should be as thin as possibly achievable.

Further. In many cases I have seen electronic components with a considerably thicker paste. Often pink, as I recall. Possibly and mostly in cases where heat generation is not as high as with CPUs, can not recall for sure. Anyway. My mind tells me that thicker pink paste, like a play-dough, can not be as thin layer as CPU-grade paste, hence worse heat conduct.

What kind of thermal paste is usually used in the industry, to convey heat from FETTs to heat sink? If the worse kind, can the thinner CPU grade paste be a viable alternative? Regardless if in this project or to enhance the BMS one already own at home.

The thought is not about enhancing in order to push through higher A, but rather staying within specs of manufacturer, but lower the working temperature, hence raising reliability of the purchased hardware.

What kind of paste are you planing to put on your BMSes?
 
I have seen thicker thermal pads used on fets (like on a high end graphics card) because they are more forgiving for minor height differences across multiple components. And FETs don't have the Instantaneous heat spikes a CPU has.
 
I interpret the 100-150a with out heat sink. But the aluminum plates are planned further in to development.

I think we are all eager and looking forward to information about maximum continuous and short term currents, with heat sink, both calculated and revised after your initial tests.
Correct, that's without any extra heat dissipation - but just passive cooling with heat sinks the board is designed to do 300a, so that's the end target. Keep in mind that we also have PWM fan headers on it, so it's possible to do active cooling with it as well but we didn't bother modeling above 300a as that's our max load. It's also worth pointing out we support from 4 to 24 cells, and from 12v up to 110v systems, although I know the higher voltage systems are less common, we wanted to be able to cover new chemistries and more future proofing.
 
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you should start a separate thread to discuss this. Post some pics.
@wpns I created a new thread to discuss it with some pics, and I'll post the STL once it's approved on the site I uploaded it to - here it is for those interested:
 
Correct, that's without any extra heat dissipation - but just passive cooling with heat sinks the board is designed to do 300a, so that's the end target. Keep in mind that we also have PWM fan headers on it, so it's possible to do active cooling with it as well but we didn't bother modeling above 300a as that's our max load. It's also worth pointing out we support from 4 to 24 cells, and from 12v up to 110v systems, although I know the higher voltage systems are less common, we wanted to be able to cover new chemistries and more future proofing.
Will this BMS be able to control something like this relay? requires 9-36V for operation. Ideally could be used as a redundant disconnect in case the BMS fails catastrophically.

 
Will this BMS be able to control something like this relay? requires 9-36V for operation. Ideally could be used as a redundant disconnect in case the BMS fails catastrophically.

It shouldn't be an issue - we have 4 relays on the board that can handle both wet (up to 30v up to 3A), and anything dry. I don't see this calling out as explicitly dry but most contactors are because of the loads they switch, and it looks like it handles an input from 8v to 30v and 100ma minimum. So you'd supply that to the relay on our board, and then our board would turn on/off the power that goes into the two wires on the contactor and you should be good to go.
 
What is the closed comms programming like? What commands are there that the bms can do?
Will it be compatible with EG4, Sol-ark, Growatt, Midnite Solar?

What do you mean by closed comms - the isolated or internal ones on our board? Or do you mean just closed loop? Just to answer them all, each comm port (RS485/CAN/RS232) are all fully isolated. We have 2x RS485's (also isolated) that we've reserved for internal communications between our products just in case - but our primary means of inter-device communications is via ethernet. One of the things we did for our cloud API was actually integrate the document generation into the code, which actually worked REALLY well (because let's face it, who likes maintaining docs), and so I'll probably look to do something similar on this as well - with the upside being that it should make working with an integrating any of our devices into other systems a breeze.

As far as communicating with other devices, I only have experience with Voltronic (who is the OEM manufacturer for a couple of those brands you listed I believe), so we already support two of their protocols, but they're the older RS232 ones and meant more for external control of their devices than for data exchange. I've done a quick look over some of the more data exchange focused protocols (usually the RS485 or CAN variants), and nothing seems that big a deal - but it's fairly low on the list, with all the focus being on core BMS functionality first.
 
So the back is also covered with components, so the heatsync will be on both the front and back - a bit like the JDB's do it, with an aluminum plate that screws down to make contact. Really it's the right side (where the battery terminals are) that needs the heat dissipation more than the left side, and we have done the thermal modeling to see how it should heat, but ultimately when it's under real load it's nice to see it happen in the real world. As I said, even at 100-150a it should be fine without heat syncs, but you wouldn't want to push it beyond that.

In terms of how it would be oriented for cases, it's designed to go into our systems, so I don't have any experience with other cases that are out there - we did match up a couple of the screw holes to a similar JK BMS, so you might be able to use the same mounting points, although the cable attachments might need to be different. We really didn't design it to be a drop in replacement for a JK or JBD, etc - so that's probably not going to be the best use case for it, you're probably better off just sticking with whatever the case is designed for. At some point we may design a rack mount case specifically for this, but that's a ways off as we do more software and hardware design work and not mechanical engineering.

FWIW, I've designed a 3D printed Eve 280-300ah prismatic cell holder, like those ABS one you can buy from China, and I'll be posting up the STL and pictures in a couple weeks for anyone who's interested in making anything like that. I print them with PETG, and assuming you're getting a decent price on your filament, it comes out to about the same cost as the Chinese ones, but when you factor in not paying for shipping it's much cheaper - plus it's fun to print them and mine have some different design elements I think are cool. We use 80/20 quite a bit, so they're designed to 'lock' into the channels on the 15 series (both from the bottom and top), and the sides of the brackets lock into eachother as well - and I just use fiber reinforced tape around it to keep it kind of locked together until it's mounted into the 80/20. On the top the channels also ensure that the 80/20 can't come in contact with the terminals, which would clearly be bad. ;)

The main reason why I asked about mounting is because: Battery boxes like Mason by Seplos and Yixiang by JK are abundant, cheap, and ready to ship. Likewise, those who currently have these battery boxes and are not satisfied with their BMSes can easily pop your BMS in and call it a day. If I need to get custom made boxes, it would take weeks/months... it would be inconvenient, too much trouble to migrate, some might not migrate at all.
 
Since this BMS uses ESP32, please support WIFI (or cloud). With it, we can monitor/manage it from anywhere. A client some 500kms away having issues? No problem: Just access it from the internet.
 
Do you have a ROM price for these? My JBD units have an issue where the contactor drops out on one of the two in parallel. I'm getting tired of it.

Before anyone tells me to set the dropout time, they are already that way. I would love a new firmware load that doesn't drop the contactor based on time.
 
Since this BMS uses ESP32, please support WIFI (or cloud). With it, we can monitor/manage it from anywhere. A client some 500kms away having issues? No problem: Just access it from the internet.
It supports both ethernet (preferred) and WiFi (works) - but for WiFi we're just using the onboard module antenna which is less than ideal. It will certainly work, but if you put it inside of something metal, forget it. As far as cloud, we have a cloud component that does monitoring but not configuration (that all must be done locally) - but my personal preference is to setup a VPN into your network like with Wireguard and then just access it like you would locally. Or if you use Home Assistant, you can see basically everything from there (but once again, with only limited ability to change things at the moment, that's all handled through our normal web interface).
Do you have a ROM price for these? My JBD units have an issue where the contactor drops out on one of the two in parallel. I'm getting tired of it.

Before anyone tells me to set the dropout time, they are already that way. I would love a new firmware load that doesn't drop the contactor based on time.
Not yet, but it's not going to be price competitive with the JBD - so you may just be better off sticking with it unless there's a specific feature we have that you want (and that might be the case with your contactor comment). We have some ability to tweak the price by not populating components, most specifically the mosfets, and that can certainly reduce the price probably more than anything, but initially we'll only be making the 300A version.
 
It supports both ethernet (preferred) and WiFi (works) - but for WiFi we're just using the onboard module antenna which is less than ideal. It will certainly work, but if you put it inside of something metal, forget it.
Here is the thing:

If I were to connect Ethernet for each and every BMS, into a hub some ~10 to 50 meters away, I might as well instead install another network hub besides my batteries and Inverters. correct?

Might as well install a WIFI router instead of an ethernet hub. . . besides, inverter's data logger require WIFI connection anyways.
 
Here is the thing:

If I were to connect Ethernet for each and every BMS, into a hub some ~10 to 50 meters away, I might as well instead install another network hub besides my batteries and Inverters. correct?

Might as well install a WIFI router instead of an ethernet hub. . . besides, inverter's data logger require WIFI connection anyways.
I'd stick a wired network switch next to them, use short patch cables from BMSes to switch, then run a single ethernet line to wherever.
 
How many independent BMS will you have?
Most of mine will be daisy chained, like for a 16s8p battery.
If assembled as one connected battery, would a long single RJ-45 cable do to communicate with all?
(Mine aggregate for inverter communications, but have separate bluetooth per BMS. Haven't tried wired connection to PC.)
 
Do you have an estimate of when these might be available to purchase? It sounds like the perfect platform for my system (and I am about to order more JBD boards, however, I might hold off if your boards will be available in the foreseeable future and within say 2x of the price of a jbd bms.)
 
Be able to accept multiple parallel RS485 as a Master, Slave 1, Slave 2... but report them as one similar to what Pace, JBD, and EG4 does. One master BMS reading all the slaves and reporting as one big battery to the inverter via CAN, RS485, and have a RS232 port to also monitor.
Look at the JBD UP16S015K BMS
 

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